Registering a Service Proxy

Consul Connect, the built-in service mesh of Consul, uses sidecar proxies to secure and manage traffic between services. By registering a sidecar proxy alongside your application, Consul can automatically route and secure calls through TLS-encrypted channels.

Note

Registering a service proxy in Consul does not launch it. You still need to start the proxy process (either Consul’s built-in proxy or an external proxy such as Envoy).

Key tasks:

Task	Description
1. Register the proxy	Add a `connect.sidecar_service` stanza in your service config
2. Start the proxy	Launch with `consul connect proxy -sidecar-for <service>`

1. Registering via Configuration File

Instead of the HTTP API, declare your sidecar proxy in the same JSON or HCL file as your primary service. Include a connect block with an empty sidecar_service object:

{
  "service": {
    "name": "front-end-ecommerce",
    "port": 8080,
    "connect": {
      "sidecar_service": {}
    }
  }
}

"name": Service identifier (e.g., front-end-ecommerce).
"port": Port your application listens on.
"connect.sidecar_service": {}: Signals Consul to register an integrated sidecar proxy.

Verify both the service and its proxy via the Consul UI or API.

2. Adding Upstream Dependencies

Declare downstream services under proxy.upstreams within the sidecar_service block:

{
  "service": {
    "id": "web-01",
    "name": "front-end-ecommerce",
    "tags": ["v7.05", "production"],
    "address": "",
    "port": 8080,
    "connect": {
      "sidecar_service": {
        "proxy": {
          "upstreams": [
            {
              "destination_name": "db01"
            }
          ]
        }
      }
    }
  }
}

"id": Unique instance identifier.
"tags": Metadata (version, environment).
"address": If empty, defaults to the local agent address.
"connect.sidecar_service.proxy.upstreams": List of target services.
- "destination_name": Consul-registered name of the downstream service.

Note

To add more dependencies, append additional objects to the upstreams list.

"upstreams": [
  { "destination_name": "db01" },
  { "destination_name": "api-service" }
]

3. Deploying and Starting the Sidecar Proxy

Place your JSON file in Consul’s configuration directory (e.g., /etc/consul.d/).
Reload or restart the Consul agent:
- consul reload
- or systemctl restart consul
Launch the proxy process:
consul connect proxy -sidecar-for front-end-ecommerce

After these steps, both the application and its sidecar proxy are registered and active. Verify connectivity in the Consul UI, via the CLI, or using the API.

References

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